Boolean Intersect - Cannot execute boolean operation
Try this:

1) In edit mode select all and remove doubles (W -> remove doubles ) when recalculate normals (Ctrl+N )

2) If it doesn't help, try newer version of Blender. It has a new Boolean solver "B-mesh" that can work with more complex geometry. 

3) Check your model with 3D-printing toolbox add-on: Checks -> Solid must output 0 manifold edges.



If it's not so, you can select all bad edges by pressing button here in edit mode: